TM 5-6640-212-14
b. Operation.
2-21. Automatic Combustible Gas Alarm and Air
(1) Set thermostatic control to desired temperature.
a.
The automatic combustible gas alarm is a
CAUTION
calibrated instrument designed to continuously monitor
for combustible gas air mixtures. It alerts personnel of
Do not allow high pressure steam
combustible mixtures that could cause explosions and
boiler to operate when steam flow is
fires, and it automatically activates an air purging system.
interrupted.
b. The alarm system consists of a main control unit
(2) Turn AUX switch on the gum bath to the ON
position.
mounted in a protected nonhazardous area and
NOTE
connects electrically to the detector assembly. The
Do not exceed service-pressure
alarm can operate using 115/230 vac, 50/60 Hz, or 12
temperature rating.
vac, with 15 watts of power. The alarm is calibrated for
propane and has a setting of 20 to 40 percent of the
(3) To shut down the high pressure steam boiler, set
lower explosive limit (lel) of gasoline. The remote
the AUX switch on the gum bath to the OFF position.
detector voltag voltage is 5.5 vdc. An indicating meter
shows the concentration level of a sample being
2-20. Low Pressure Steam Boiler. Description. The
monitored, and adjustable dual-level alarm circuits are
low pressure steam boiler (fig. 2-12) is located in the
triggered whenever a concentration exceeds the preset
front compartment of the semitrailer, on the left side as
level (lel).
you enter the compartment. The low pressure steam
boiler is used to preheat water from the water tank to the
c. The cabinet assembly houses the electronics and
high pressure steam boiler which is used with the gum
control circuits necessary for instrument operation.
bath. The low pressure steam boiler has its own
Incoming power and detector leads enter the cabinet
through 3/4 inch conduit fittings. The controls, fittings,
water from the water tank, or external water supply; if
and connections are discussed below.
tank or external water supply is under pressure,
(1) Green Pilot Light. When the instrument power is
circulator pump need not be turned on. The boiler is
on and the detector circuit is energized, the green pilot
light comes on.
and glass sight glass. The automatic water feeder
(2) Blue Fail Light. When there is equipment failure
system (fig. 2-15) will automatically fill boiler to proper
or malfunction, the blue fail light comes on.
level and shut off the water when an internal float valve
(3) Amber Warn Light. The amber warn light comes
closes when proper water level is reached. The low
on when a combustible gas condition exceeding the low
pressure boiler also contains a pressure gage, pressure
alarm setting exists at the remote detector, or when the
cut-off switch and a pressure release valve to protect the
alarm test switch ((e) below) has been actuated.
boiler from damage if boiler pressure is too high, or water
(4) Red Alarm Light. The red alarm light comes on
level is too low. Circuit breakers for the pressure steam
when a combustible gas condition exceeding the high
boiler, high pressure steam boiler and gum bath must be
alarm setting exists at the remote detector, or when the
turned on for use. After tests are completed, open drain
alarm test switch has been actuated.
(5) Alarm Test Switch. The alarm test switch is a
water from boiler then close valve. Turn off circuit
momentary contact pushbutton switch incorporated with
breakers.
the warn light. When it is depressed electrically, there is
a simulation of an alarm level of gas concentration at the
CAUTION
remote detector. This switch provides a functional check
If trailer is to be stored in an area
of the analyzer and remote alarm circuit.
where the temperature will be below
freezing and no heat supplied, be
sure to drain all water from system to
prevent damage to boiler.
2-26